This invention relates to a floating-caliper spot-type disc brake for automotive vehicles whose brake housing is a light-metal casting reinforced by means of bolts or sleeves of a high-tensile material.
It is a general object to reduce the weight of automotive vehicles in order to reduce fuel consumption. One particular interest is to keep the unsprung masses, arranged at the vehicle wheel, as small as possible in order to improve driving. It is for these reasons that light-metal construction becomes more and more important for vehicle brakes.
In some spot-type disc brakes, a U-shaped floating caliper transmits the high clamping force required for pressing the brake shoes to the brake disc. In such an action, a caliper bridge straddling the brake disc is exposed to high bending loads. The floating caliper must have a great stiffness to prevent it from bending up in an unduly wide manner. On the other hand, the radial assembly space between the outside edge of the brake disc and the wheel rim is limited. Therefore, there exists the need of providing a high-tensile material with a high elasticity modulus for the floating caliper. The use of cast iron or similar high-tensile materials is widely accepted. These materials, however, have a relatively high specific weight. Light metals such as aluminum or light alloys, however, have little elasticity moduli. This is at least the case when the material price is to be within economically justifiable limits.
Now, from the German Published Patent Application DE-OS No. 29 50 660, for instance, there are known spot-type disc brakes with a light-metal floating caliper where areas of the caliper housing that are subject to particularly strong loads are reinforced with cast-in inserts of a high-tensile material. The disadvantage of these caliper housings is that the inserts are completely Jacketed by light-metal, with the surface zones which are neighboring on the brake disc and which are particularly subject to great tension load being of light metal. Moreover, due to their shape adapted to the floating caliper, the inserts must be specifically manufactured for this purpose which causes relatively high additional costs.
In a generic disc brake known from German Published and Examined Patent Application DE-AS No. 12 86 845 the floating caliper is reinforced by a screw bolt arranged in an axially parallel bore of the caliper bridge. Disadvantageously, in this arrangement, the bolt is not arranged in the area of the caliper bridge which is subject to particularly strong tension load and which is directly neighboring on the radially outside edge of the brake disc and on the brake shoes. Moreover, a special bolt is used which features a complicated design and, thus, is expensive.